blink: Add backdrop-filter support

Source/modules/canvas2d/CanvasRenderingContext2DState.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 
 #include "modules/canvas2d/CanvasRenderingContext2DState.h"
 
 #include "core/css/CSSFontSelector.h"
 #include "core/css/resolver/FilterOperationResolver.h"
@@ skipping 18 matching lines @@
 CanvasRenderingContext2DState::CanvasRenderingContext2DState()
     : m_unrealizedSaveCount(0)
     , m_strokeStyle(CanvasStyle::createFromRGBA(SK_ColorBLACK))
     , m_fillStyle(CanvasStyle::createFromRGBA(SK_ColorBLACK))
     , m_shadowBlur(0)
     , m_shadowColor(Color::transparent)
     , m_globalAlpha(1)
     , m_lineDashOffset(0)
     , m_unparsedFont(defaultFont)
     , m_unparsedFilter(defaultFilter)
+    , m_unparsedBackdropFilter(defaultFilter)
     , m_textAlign(StartTextAlign)
     , m_textBaseline(AlphabeticTextBaseline)
     , m_direction(DirectionInherit)
     , m_realizedFont(false)
     , m_isTransformInvertible(true)
     , m_hasClip(false)
     , m_hasComplexClip(false)
     , m_fillStyleDirty(true)
     , m_strokeStyleDirty(true)
     , m_lineDashDirty(false)
@@ skipping 29 matching lines @@
     , m_shadowAndForegroundDrawLooper(other.m_shadowAndForegroundDrawLooper)
     , m_shadowOnlyImageFilter(other.m_shadowOnlyImageFilter)
     , m_shadowAndForegroundImageFilter(other.m_shadowAndForegroundImageFilter)
     , m_globalAlpha(other.m_globalAlpha)
     , m_transform(other.m_transform)
     , m_lineDash(other.m_lineDash)
     , m_lineDashOffset(other.m_lineDashOffset)
     , m_unparsedFont(other.m_unparsedFont)
     , m_font(other.m_font)
     , m_unparsedFilter(other.m_unparsedFilter)
+    , m_unparsedBackdropFilter(other.m_unparsedBackdropFilter)
     , m_filterValue(other.m_filterValue)
     , m_resolvedFilter(other.m_resolvedFilter)
+    , m_backdropFilterValue(other.m_backdropFilterValue)
+    , m_resolvedBackdropFilter(other.m_resolvedBackdropFilter)
     , m_textAlign(other.m_textAlign)
     , m_textBaseline(other.m_textBaseline)
     , m_direction(other.m_direction)
     , m_realizedFont(other.m_realizedFont)
     , m_isTransformInvertible(other.m_isTransformInvertible)
     , m_hasClip(other.m_hasClip)
     , m_hasComplexClip(other.m_hasComplexClip)
     , m_fillStyleDirty(other.m_fillStyleDirty)
     , m_strokeStyleDirty(other.m_strokeStyleDirty)
     , m_lineDashDirty(other.m_lineDashDirty)
@@ skipping 65 matching lines @@
 
 void CanvasRenderingContext2DState::fontsNeedUpdate(CSSFontSelector* fontSelector)
 {
     ASSERT_ARG(fontSelector, fontSelector == m_font.fontSelector());
     ASSERT(m_realizedFont);
 
     m_font.update(fontSelector);
     // FIXME: We only really need to invalidate the resolved filter if the font
     // update above changed anything and the filter uses font-dependent units.
     m_resolvedFilter.clear();
+    m_resolvedBackdropFilter.clear(); // TODO(hendrikw): Not so sure if this is needed.
 }
 
 DEFINE_TRACE(CanvasRenderingContext2DState)
 {
     visitor->trace(m_strokeStyle);
     visitor->trace(m_fillStyle);
     visitor->trace(m_filterValue);
+    visitor->trace(m_backdropFilterValue);
     CSSFontSelectorClient::trace(visitor);
 }
 
 void CanvasRenderingContext2DState::setLineDashOffset(float offset)
 {
     m_lineDashOffset = offset;
     m_lineDashDirty = true;
 }
 
 void CanvasRenderingContext2DState::setLineDash(const Vector<float>& dash)
@@ skipping 108 matching lines @@
     if (m_realizedFont)
         static_cast<CSSFontSelector*>(m_font.fontSelector())->unregisterForInvalidationCallbacks(this);
 #endif
     m_font = font;
     m_font.update(selector);
     m_realizedFont = true;
     selector->registerForInvalidationCallbacks(this);
     // FIXME: We only really need to invalidate the resolved filter if it
     // uses font-relative units.
     m_resolvedFilter.clear();
+    m_resolvedBackdropFilter.clear(); // TODO(hendrikw): Not so sure if this is needed.
 }
 
 const Font& CanvasRenderingContext2DState::font() const
 {
     ASSERT(m_realizedFont);
     return m_font;
 }
 
 void CanvasRenderingContext2DState::setTransform(const AffineTransform& transform)
 {
@@ skipping 28 matching lines @@
         filterEffectBuilder->build(styleResolutionHost, filterStyle->filter(), effectiveZoom);
 
         SkiaImageFilterBuilder imageFilterBuilder;
         RefPtrWillBeRawPtr<FilterEffect> lastEffect = filterEffectBuilder->lastEffect();
         m_resolvedFilter = imageFilterBuilder.build(lastEffect.get(), ColorSpaceDeviceRGB);
     }
 
     return m_resolvedFilter.get();
 }
 
+SkImageFilter* CanvasRenderingContext2DState::getBackdropFilter(Element* styleResolutionHost, const Font& font) const
+{
+    // TODO(hendrikw): Better understand what this function is doing and determine if we can reuse getFilter,
+    // of if this function needs to be modified.
+    if (!m_backdropFilterValue)
+        return nullptr;
+
+    if (!m_resolvedBackdropFilter) {
+        RefPtr<ComputedStyle> filterStyle = ComputedStyle::create();
+        // Must set font in case the filter uses any font-relative units (em, ex)
+        filterStyle->setFont(font);
+
+        StyleResolverState resolverState(styleResolutionHost->document(), styleResolutionHost, filterStyle.get());
+        resolverState.setStyle(filterStyle);
+
+        // TODO(junov): crbug.com/502877 Feed m_fillStyle and m_strokeStyle into FillPaint and
+        // StrokePaint respectively for filters that reference SVG.
+        StyleBuilder::applyProperty(CSSPropertyBackdropFilter, resolverState, m_backdropFilterValue.get());
+        RefPtrWillBeRawPtr<FilterEffectBuilder> filterEffectBuilder = FilterEffectBuilder::create();
+        const float effectiveZoom = 1.0f; // Deliberately ignore zoom on the canvas element
+        filterEffectBuilder->build(styleResolutionHost, filterStyle->filter(), effectiveZoom);
+
+        SkiaImageFilterBuilder imageFilterBuilder;
+        RefPtrWillBeRawPtr<FilterEffect> lastEffect = filterEffectBuilder->lastEffect();
+        m_resolvedBackdropFilter = imageFilterBuilder.build(lastEffect.get(), ColorSpaceDeviceRGB);
+    }
+
+    return m_resolvedBackdropFilter.get();
+}
+
 SkDrawLooper* CanvasRenderingContext2DState::emptyDrawLooper() const
 {
     if (!m_emptyDrawLooper) {
         OwnPtr<DrawLooperBuilder> drawLooperBuilder = DrawLooperBuilder::create();
         m_emptyDrawLooper = drawLooperBuilder->detachDrawLooper();
     }
     return m_emptyDrawLooper.get();
 }
 
 SkDrawLooper* CanvasRenderingContext2DState::shadowOnlyDrawLooper() const
@@ skipping 66 matching lines @@
     m_shadowColor = shadowColor;
     shadowParameterChanged();
 }
 
 void CanvasRenderingContext2DState::setFilter(PassRefPtrWillBeRawPtr<CSSValue> filterValue)
 {
     m_filterValue = filterValue;
     m_resolvedFilter.clear();
 }
 
+void CanvasRenderingContext2DState::setBackdropFilter(PassRefPtrWillBeRawPtr<CSSValue> filterValue)
+{
+    m_backdropFilterValue = filterValue;
+    m_resolvedBackdropFilter.clear();
+}
+
 void CanvasRenderingContext2DState::setGlobalComposite(SkXfermode::Mode mode)
 {
     m_strokePaint.setXfermodeMode(mode);
     m_fillPaint.setXfermodeMode(mode);
     m_imagePaint.setXfermodeMode(mode);
 }
 
 SkXfermode::Mode CanvasRenderingContext2DState::globalComposite() const
 {
     SkXfermode* xferMode = m_strokePaint.getXfermode();
@@ skipping 70 matching lines @@
         paint->setLooper(0);
         paint->setImageFilter(shadowAndForegroundImageFilter());
         return paint;
     }
     paint->setLooper(shadowAndForegroundDrawLooper());
     paint->setImageFilter(0);
     return paint;
 }
 
 } // blink